Truck idles rough and wants to die the more I shut off and start it (say, on a day when I'm running a bunch of errands - and it's worse when it's warm out). Always the scent of unburned fuel in the exhaust. Adjusting the timing made little difference. It doesn't really respond to mixture adjustments, and I haven't had any luck tracking down a vacuum leak. Electrical/spark issues have been ruled out. I've been toying with the idea of a carburetor rebuild and noticed this when I was poking around today (see photo)...

What exactly might be leaking? Is this a sure indication that the carb rebuild is a good idea?

'84 2wd truck has 165,000 miles, and I've had it the last 20,000.

 

Is that on the intake manifold? If so it looks like it might be the vaccum to the brake booster

 

Intake manifold, yes, and thanks for pointing out what that connection likely is - I had wondered. But I assumed it was fuel leaking from above. The fast idle screw is coated in it, too (it's just above that spot, but you can't see it behind the hose in that photo). I was curious if there was a seal on the carb that gave out. Even if it's not related to my problem, it would be good to know if the carb rebuild is needed, regardless.

 

Looks more like oil.